KR19980701974A - Point-to-multipoint broadband service drop with multiple time slot return channels for consumer premise - Google Patents

Abstract

The remote site in the communication system is connected to an optical network portion that is ported to the optical fiber link through a multidrop communication link consisting of an unshielded twisted pair. In order to transmit the downlink wideband information signal from the master site 10 to the optical network to the remote site and to prepare for a return message from the remote site, a point-to-multipoint communication scheme is provided. According to this scheme, the upstream transceiver in the optical interface section includes an STS-1 frame containing a wideband information signal to be given to one or more remote sites, and a control code of a representative return time slot associated with each destination remote site through multidrop communication. To the remote site. At the remote site, the downstream transceiver uses its representative return time slot control code to control its transmission time on the uplink slotted bus return channel.

Description

Point-to-multipoint broadband service drop with multiple time slot return channels for consumer premise

Field of invention

The present invention generally relates to an optical network interface where a number of subscriber premises having one or more user devices, such as digital video terminals, define a downstream end of the broadband, an optical fiber transmission highway, an upstream end of the broadband connected to the broadband service master site. The present invention relates to an optical fiber telecommunication system. In particular, in addition to performing telephony, the present invention relates to a point-to-multipoint broadband service drop that connects an optical network interface to a user premise that requires and receives a selected television channel.

Background of the Invention

US Patent 5,150, 247 invented by the title Fiber Optic Telecommunication System Employing Continuous Downlink, Burst Uplink Transmission Format with Preset Uplink Guard Band, R. Sharpe, issued September 22, 1992 (hereafter assigned to the assignee of the present application, Its detailed description is referred to as the '247 patent, incorporated herein by reference, and the optical fiber (or fiber-in-the-loop (FITL) communication system is a conventional' copper 'telephone network and' It is designed as a broadband alternative to various telecommunications networks, such as add-on 'cable television networks (which use separate, dedicated conductor coaxial cables).

Unfortunately, the cost of meeting a system designed for a broadband network is relatively expensive due to the fact that such schemes often use multiple optoelectronic and interconnect devices such as sources and detectors. When added to the cost of splices for optical connectors and optical fiber links and the number of optical fibers of their own in the wiring cable between the ends of the opposing links, such a number of devices have a strong impact on the overall system cost. As a result, for one subscriber, the total cost of the device is not only two transceiver pairs per subscriber, but also a large fraction of the price tag for a premise system that conventionally uses a separate, dedicated pair of optical fibers in the wiring cable for each subscriber. .

One approach to reducing the costly cost of optical fiber devices required for this system has been to design signal processing and communication architectures that handle multiple subscriber lines per unit and can use highly compressed data formats. Unfortunately, such an approach is virtually self-destructive, in order to widen the cost of optical fiber devices on multiple subscribers, because this system architecture becomes very complex and exacerbates the cost problem rather than mitigating it.

To solve this problem, the optical fiber telecommunication method described in '247 uses a time division multiple communication method in which a plurality of television and telephone signals are transmitted in a continuous time division format in the downstream direction, but a channel selection request and a user premise device are required. Telephone signals from are transmitted downstream in the form of slot bursts.

In particular, referring to FIG. 1, as shown schematically in the '247 patent approach, a host digital terminal (HDT) to which telephone and video signals are supplied at the master site 10 is connected to a plurality of remotes by an optical fiber cable pair 20. It is linked to a geographically separated subscriber site. Telephony messages in the downstream direction (such as supplied by the central office switch 14 via the link 12 and by a representative television channel digital signal 18 encoded via the link 16). Signal) is transmitted via the first optical fiber 12 in a continuous mode time division multiplex form at the master site 10 to the splitter site 23 located downstream from the host digital terminal.

Splitter site 23 is located at the second common 'join' point on optical splitter 26 and uplink fiber 22 located at multiple fanout, first common 'split' points on downlink fiber 21. And positioned multiple feed-in optical coupling devices 27. These fibers, i.e., downlink and uplink fiber pairs 21, 22, that join the connections in the splitter site, are connected through the associated broadband service drop 35 by respective downlink and uplink fiber links 24, 25, respectively. It is connected to a plurality of subscriber interface optical network units 30 serving one or more related subscriber premises 40.

Each television channel in a digitally formatted telecommunications signal frame in the downlink direction transmitted on the downlink fiber 21 from the master site 10 is transmitted on the uplink fiber 22 from the user premise. Included in the link burst message, these channels are selected in response to subscriber channel requests. Each downlink message categorizes the optical network portion 30 intended for this message and specifies that a digital subscriber line packet is delivered directly to it. The receiving optical network section 30 demultiplexes the contents of the message and transmits each television channel signal and telephone signal to the television set 43, the switching handset (not shown), etc., at the destination site 40, and the like. Route to a user premise device (CPE), such as a set top decoder 41.

Burst transmission from the user premise in the upstream direction to the master site occurs in a time division multiple access format. In a pre-allocated time slot of successive uplink burst cycles, the subscriber site is given the opportunity to transmit a digital subscriber line data packet containing samples of the telephone channel. Each uplink burst cycle may include additional time slots that can be accessed by subscriber interface sites based on competition principles for network control and television related signals.

While the communications described in the '247 patent provide significant improvements to the previously proposed broadband system, the typical continuous time division multiple format used for downstream messages and the slot burst upstream format for upstream messages are all service providers. May not necessarily be used or desirable. Indeed, the first '247' wideband telecom industry is an internationally accepted standard suitable for the transmission of various types of data, in particular synchronous optical network transport (SONET) stream (STS) base transmissions where asynchronous transfer mode (ATM) data cells are transmitted. Since the invention has been invented, the slot bus return channel can still be used from the user premise device.

Summary of the Invention

In accordance with the present invention, the premise of a plurality of users with such an internationally accepted reference format of communication, in particular the selector of the STS-1 frame, is used to provide timing criteria for providing uplink burst transmission opportunities to the associated CPE along the drop. The system described in '247 above was modified to extend the use of a point-to-multipoint asynchronous transmission mode (ATM) transmission criterion in which an ATM cell capsule sealed STS-base signal is broadcast to the device. The logical frame structure of the STS-1 frame includes a multibyte transmission overhead portion consisting of a line overhead portion and a section overhead portion. Within this section overhead are F1 bytes that can be used for a limited purpose of the user. This F1 byte is used by each optical network portion and circuitry in the user's device as a reference for the slot bus return channel.

The transmission overhead portion of the STS-1 frame comes before the Synchronous Payload Envelope (SPE). The point-to-multipoint asynchronous transmission mode (ATM) transmission cell is encapsulated in the SPE of the STS-1 frame. The format of the slot bus return channel is to allow each of the plurality of STS-1 frames to be separated into multiple time slots sufficient to accommodate upstream signal traffic from the multipoint drop. The fact that an asynchronous transfer mode cell and associated overhead can be transmitted during one of the time slots is that the data rate of the channel in the uplink direction is large enough.

As in the system described in the '247 patent, the distance between the optical network portion and each CPE is different from node to node, so that the transmission time of the timing reference transmitted from the downlink STS signal by the optical network portion is different for each CPE. The same transmission offset occurs for the return channel. To prevent collisions with the return channel of other CPEs, guard bands are inserted at the front end of consecutive time slots on the uplink channel. This guardband is sized to accommodate the worst case round trip transmission time difference between CPEs, and prepares for any change in CPE latency.

The front end of each data segment of the uplink slot return burst includes a multibyte ATM cell header, an ATM cell payload segment and burst monitor followed by a binary interleaved parity byte (BIP8). The return channel burst header contains a predetermined binary pattern preamble used by the phase alignment receiving device, a sync byte (sync word), and other information for link management.

The ATM base point-multipoint wideband drop return channel control mechanism of the present invention has the advantage of internationally accepted protocols and signal formats that define a standardized layered interface model with physical / electrical (PHY) and ATM layering. . The PHY layer provides electrical interface, framing, synchronization, and accessibility of the interface, while the ATM layer performs packet segmentation and reassembly. The ATM Forum Standards Committee defined an interface between the ATM layer and the PHY layer called the Universal Test and Operations PHY Interface (UTOPIA) for ATM, which would support multiple PHY layers from a common ATM layer. will be.

In accordance with the present invention, the optical network portion of the system of the '247 patent is modified to provide an ATM cell embedded STS signal format. The downlink end of the optical network section, which interfaces with the optical receiver connected to the downlink fiber link from the splitter site, demultiplexes the telephone and control channels with the telephone / control demultiplexer section or the mux / demux section and the ATM cell with the ATM interface. The demultiplexer is applied to a demultiplexer.

ATM cells arriving at the ATM interface are filtered, buffered and applied to the UTOPIA bus with associated cell routing information based on the ATM cell address. The one or more PHY units attached to the UTOPIA bus will receive cells based on the relevant cell routing information. This ATM interface provides the upstream or return channel signal to the mux / demux section upstream multiplexer. The output of the upstream multiplexer is connected to an optical transmission device that drives the upstream transmission fiber.

In the physical interface substrate, the PHY portion is coupled to the UTOPIA interface and provides a physical interface to the ATM cell stream. This PHY section is coupled to a hybrid circuit that allows bidirectional transmission on a single unshielded twisted pair (UTP) through each transmit and receive filter in both directions. The receive filter does not accept noise and interference in the received signal, but the transmit filter band-limits the transmitted signal.

Each PHY unit has an upstream (relative to UTP) transceiver with a rate adapting, transmit first in, first out (FIFO) buffer to which the broadband service drop ATM data streams input from the UTOPIA interface are connected. This elastic buffer is read at a rate associated with the output data rate of that port. The read clock signal is derived from the timing generator and the read enable signal is derived from the STS-1 framing section. This timing generator receives the STS-1 reference clock from the UTOPIA interface. The multiplexer receives the STS-1 reference clock from the transmit FIFO with the start of the associated cell indication. The second input to the multiplexer is stored in auxiliary storage and receives a 'blank' cell with no cells waiting in the transmit FIFO. This multiplexer also generates and inserts a cell header in the form of a header error correction code (HEC).

The ATM cell payload output of this multiplexer is scrambled so that the user equipment prevents false cell detection at the receiver. This scrambled ATM data cell is then inserted into the STS-1 frame by the STS-1 framer. The timeslot counter, which references the subdivided framing clock, provides a timing signal for inserting a user-definable F1 byte within the STS-1 frame.

As mentioned above, the F1 byte is used as the time slot assignment identifier for the bus return channel slotted from the CPE device. The STS-1 frame was then scrambled by a SONET frame synchronous scrambler and connected to a carrierless amplitude modulation, phase modulation (CAP) encoder for transmission to the user equipment via UTP.

On the receive side of the PHY transceiver portion of the ONU, the output of the receive filter is coupled to a CAP decoder that demodulates a CAP modulated signal burst received from the user premise device for the number of active slots in the return, uplink channel. The scrambled return channel burst from the CPE is descrambled and applied to a burst demultiplexer that demultiplexes the ATM cell from the return channel burst overhead. The demultiplexed portion of the burst header is connected to the associated header data register, the contents of which are monitored by the controlling microprocessor. The cell router / filter unit routes ATM data cells in the received return channel burst to a receive FIFO that is read by a signal from the UTOPIA interface, such as the ONU's transmit FIFO.

The communication unit included in the user premise device such as the television set top box is also modified to prepare for the above-described ATM cell embedded STS signal format. The downlink end of the UTP or coaxial cable is ported to the hybrid circuit to allow bidirectional transmission on an unshielded twisted pair. As in the optical network section, the receive filter does not accept out-of-band energy from the received signal, and the transmit filter suppresses the transmitted signal potentially interfering with the out-of-band emission. The output of the receive filter is connected to the downlink (relative to UTP or coaxial cable), the CPE resident PHY transceiver. The PHY part of the CPE is connected to the ATM signal processing part via the UTOPIA interface. The output of the ATM section is connected to a broadband interface device such as a Moving Pictures Experts Group (MPEG) decoder for driving the associated video device.

Like the PHY transceiver portion of the ONU (upstream), the CPE resident (downstream) transceiver PHY portion has a CAP decoder that demodulates the modulated wideband data stream received from the upstream optical network portion (16 CAP) and generates a return channel slot burst. The recovered clock is connected to various circuit elements including a clock divider that generates a subdivided clock for use. The received data stream is connected to an STS-1 framer that fits the received SONET frame and performs a bit interleaved parity (BIP8) check on the data. Keep counting some errors.

The STS-1 framer references the recovered clock to provide a receive byte clock to the downstream signal processing device. The scrambled SONET data frame descrambles the downlink signal and is coupled to an STS-1 descrambler that couples the descrambled signal to the F1 byte detector. The F1 byte detector extracts F1 bytes from the descrambled STS-1 frame overhead and connects the detected F1 bytes to the F1 byte comparator. This comparator uses the F1 byte to control the operation of the slotted return channel.

The data frame is also coupled to an ATM cell payload processor using a pointer in the STS-1 overhead portion to specify a SONET synchronous payload envelope containing the actual (ATM) data payload. Thus, the data payload is descrambled and connected to the receive FIFO controlled by the signal on the UTOPIA interface. The ATM data cell output of the receiving FIFO is connected to the UTOPIA interface for application to the ATM cell processing portion of the CPE device.

For a return channel where the user selects a television channel, for example, a speed adaptation, transmission FIFO is connected to receive an ATM cell from the UTOPIA interface. The read clock for the transmit FIFO is derived from a clock divider that references the recovered clock at the receive side, and the read enable signal is derived from the F1 byte comparator. The data output path of the transmit FIFO is connected to a logic circuit that generates and inserts a cell header in the form of a header error correction code (HEC). HEC insertion logic is coupled to the cell gap seal that convenes an uplink return time slot containing overhead. The bit error indication is linked to the cell capsule seal as part of the performance monitoring status byte containing information related to the status of the CPE.

The output of the cell capsule sealing part is connected to an ATM self-synchronizing scrambler that scrambles the ATM cell payload to prevent false cell detection at the receiving device included in the user premise device. The output of the self-synchronizing scrambler is connected to a CAP encoder (e.g., 4 CAP encoder) which is clocked by a subdivided clock signal derived from the recovered clock and is enabled by the transmit enable signal supplied from the comparator.

As mentioned above, according to the present invention, the F1 byte is used as a time slot identifier for a bus return channel slotted from a CPE access device. In response to detecting the F1 byte, the F1 byte comparator provides a control transmission enable signal when a return time slot occurs on the uplink channel. Thus, 4 CAP uplink slot transmissions occur in bursts controlled by the F1 bytes detected in the downlink STS-1 frame.

The generation time of the transmit enable signal generated by the comparator is derived by simultaneously generating the local CPE ID assigned to the CPE initialization phase and the CPE ID received in the F1 byte. The output of the 4 CAP encoder is connected via a driver to a transmission filter for application to unshielded twisted pair or coaxial cable via hybrid circuits.

The initial time slot may be obtained by excluding one of the time slots of the return channel in the initial time slot competition using, for example, an Aloha competition scheme. Providing time slots for competition prevents newly connected CPEs from interfering with CPEs that are already in use. Once a newly connected CPE obtains a time slot, the assigned time slot may be used to request additional time slots as needed. The multidrop communication mechanism of the present invention can flexibly accommodate current signal drops from which signals are supplied from various service providers.

For this purpose, a diplexer may be used to interface the unshielded twisted pairs of multidrop links from the optical network section with telephone and cable television signal ports generally installed in the user's premises. The higher frequency diplexer has a first upstream port to which UTP is connected from the optical network section and a second upstream port to which a coaxial cable used by a cable television service provider for carrying analog cable television signals to subscribers is connected. . The diplexer also includes a first downstream, telephone signal port to which a twisted pair for the user complete telephone apparatus may be connected. It additionally includes a second downstream, coaxial cable port to which a television set top box or standard cable ready television set may be connected.

This diplexer is operative to connect the downstream 16 CAP modulated STS-1 base communication signal and analog cable television signal received on the unshielded twisted pair from the optical network interface to its downstream wideband coaxial cable output port. do. This coaxial cable port may be connected to the coaxial cable fanout connector to provide multiple coaxial cable feeds to one or more user devices such as set top boxes, VCRs, and cable ready television sets. The diplexer may also be operable to connect a telephone signal received on a multidrop twisted pair from the optical network section to its downstream telephone port.

In the downstream direction, the diplexer connects the 4 CAP modulated ATM cell slotted bus communication signal in the downstream direction from the CPE-resident PHY portion of the set top box and the telephone signal applied to the unshielded twisted pair. Frequency spectrum separation of the 16 CAP in the downlink direction and the 4 CAP communication signal in the upstream direction are each separated below the band of the analog cable television signal supplied by the cable television service provider.

1 is a schematic representation of a wideband optical fiber communication system as described in U. S. Patent No. 5,150, 247, invented by Sharpe et al.

2 is a diagrammatic representation of the logical structure of an STS-1 frame.

FIG. 3 shows Table 1 in which definitions of the transmission overhead of the STS-1 frame of FIG. 2 are written.

4 is a diagram showing the format of a slot bus return channel generated by an optical network section in accordance with a received STS-1 data stream input at the downstream end of the optical fiber link.

5 is a diagrammatic representation of a portion of an optical network portion of a system of the '247 patent incorporating a modification in accordance with the present invention to provide an ATM cell embedded STS signal format.

6 is a diagram schematically showing the configuration of the PHY unit 140 of FIG.

7 is a diagram showing the configuration of a communication unit incorporating a change according to the present invention to provide an ATM cell embedded STS signal format when included in a user premise device such as a television set top box.

8 is a diagram schematically showing the configuration of each CPE-resident PHY unit 320 of the CPE communication unit of FIG.

Figure 9 diagrammatically illustrates how an unshielded twisted pair multidrop link from an optical network section is interfaced with telephone and cable television signal ports typically provided at or near the user's premises.

10 is a diagrammatic representation of the coupling of the diplexer of FIG. 9 to a coaxial cable fanout connector portion that provides multiple coaxial cable feeds to one or more user devices such as set top boxes, VCRs, and cable ready television sets.

11 shows frequency spectrum separation of downlink direction 16 CAP and upstream direction 4 CAP STS-1 base communication signals and their dual separation at the bottom of the band of analog cable television signals supplied by the cable television service provider.

details

Prior to describing in detail the ATM cell embedded STS-1 base broadband service drop according to the present invention, the present invention effectively first changes the associated control software and designated hardware subsystem elements of the system described in the aforementioned '247 patent. It belongs to doing. Thus, the configuration of this system element and the method of interfacing with other communication devices of the telecommunications network are shown in an easily understandable block diagram showing only these detailed descriptions belonging to the present invention. Thus, the block diagram of this figure shows the main elements of a system that are conveniently functionally classified, thereby making the present invention easier to understand.

As briefly described above, each STS-1 frame shown in FIG. 2, a logical frame structure, is composed of a line overhead portion 53 (9 bytes) and a section overhead portion 55 (18 bytes). A byte (9 bytes in 3 bytes) transfer overhead portion 51 (a definition described in Table 1 shown in FIG. 3) is included. Within section overhead portion 55 is an F1 byte that can be used for a limited purpose of the user. The F1 byte is used by each optical network section 30 as a reference for the slot bus return channel.

The transmission overhead 51 precedes the synchronous payload envelope (SPE) 61, the front end of which is divided by a plurality of payload segments 64, 66, 68) is the preceding (9 byte) path overhead portion 63 (a definition described in Table 1). For the 86-byte payload section, each of the nine bytes described above, there are 756 cuts of 784 bytes available for the data. A point-to-multipoint asynchronous transmission mode (ATM) transmission standard cell may be transmitted in this SPE payload section. For the frame structure shown in Fig. 2, the bytes are transmitted from left to right and from top to bottom. The bits in each byte are sent in order from the most important to the least important.

4 diagrammatically shows the format of a slot bus return channel generated by an optical network section in accordance with a received STS-1 data stream input at the downstream end of the optical fiber link. In a slot bus network, cycles or repeating time intervals in the form of slot buses are separated by an integer number of some predetermined time slot, and nodes according to this slot bus (in this case, CPEs) have a predetermined duration of available time slots. Are allowed to transmit. Various mechanisms such as Aloha, Slot Aloha Reservation Aloha, and Packet Reservation Multiple Access (PRMA) to control access to this bus are available, but time slots are acquired. The latter approach is preferred because capacity is generated by retaining that slot until one node completes the transmission. Unallocated time slots will struggle to provide on demand bandwidth.

To provide a non-limiting example, the duration of the input STS-1 frame will be considered 125 μsec. Using an example cycle period of 24 milliseconds, 192 STS-1 frame periods may be available for the return channel. This cycle period is separated into a substantial number of time slots TS1 ... TSN to accommodate upstream signal traffic from the multipoint drop. As an unlimited example, using N = 64 time slots TS1-TS64 results in each time slot with three STS-1 frames having a duration of 375 μsec.

The data rate of the uplink channel must be large enough so that the asynchronous transmission mode cell and associated overhead can be transmitted during each one of the 64 time slots. For this purpose, the uplink channel data rate is achieved at a fixed fraction of the STS bit clock rate of 51.84 MB / s, for example at a clock rate of 1/32, so that the uplink slot data rate of 1.62 Mb / s. To provide.

As described in the '247 patent, since the distance between the optical network portion and each CPE is different from node to node, the transmission time of the timing reference derived from the downlink STS signal by the optical network portion and transmitted to each CPE is It will be different for each CPE. To prevent collision with the return channel of another CPE, guard band 71 is inserted at the front end of consecutive time slots on the uplink return channel. The duration of the guard band 71 is established according to the transmission distance representing the largest difference on the twisted pair link between the optical network section and the CPE. That is, guard band 71 is sized to accommodate the worst case round trip transmission time difference between CPEs, and includes preparation for any modification in CPE latency. For the parameters of this embodiment, providing a guardband period of 79 μsec would allow for 296 μsec ATM cell data burst segment period or 60 bytes of ATM cell data per return channel time slot.

The front end of each 296 μsec data segment 72 has a (5 byte) cell header 75, an ATM cell payload segment 77, and a burst header 73 preceding the binary interleaved parity byte (BIP8) 78. As shown in FIG. 4. The burst header 73 includes a (3-byte) preamble 81 which is a defined binary pattern used by the receiver for phase alignment. This burst header comes before the sync byte or sync word 83 and two other bytes 85 for link maintenance and other functions. The BIP8 byte is used for error monitoring. The ATM cell payload segment 77 provides 48 bytes of data, yielding a total of 60 bytes of the return channel per time slot.

As briefly described above, the point-multipoint wideband drop return channel control mechanism of the present invention is ATM-based and has the advantages of internationally accepted protocols and signal formats, its standard configuration being a layered interface model, hereinafter. The physical / electric (PHY) and ATM layers described in The PHY layer provides the interface, framing, synchronization, and accessibility of the interface, while the ATM layer performs packet segmentation and reassembly (packetization). The standards committee, known as the ATM Forum, defined the interface between the PHY layer and the ATM layer, called the Universal Test and Operation PHY Interface (UTOPIA) for ATM. The UTOPIA interface will support multiple PHY layers from a common ATM layer. As a non-limiting example, the standard ATM interface uses STS-3c, DS3, STS-1 100 Mb / s multimode fiber (FDDI physical layer), DS2 and 25.92 Mb / s. An 8-bit UTOPIA interface can support up to 155 Mb / s data rates, and a 16-bit interface can support higher data rates.

5 diagrammatically shows a portion of an optical network portion of a system of the '247 patent incorporating a transceiver change in accordance with the present invention to prepare for an ATM cell embedded STS signal format. The optical fiber input to the optical network section interfaced with the optical receiver connected to the downlink fiber link 24 from the pedestal 23 connects the telephone / control channel on the link 105 to the telephone / control demultiplexer of the mux / demux section 104. It is demultiplexed with section 107 and applied as an input 101 to a high speed demultiplexer 103 that operates to demultiplex the ATM cells on the link 111 with the ATM interface 112. ATM interface 112 provides a return or upstream direction signal on link 113 to upstream multiplexer portion 109 of mux / demux portion 104. The ATM interface 112 then transmits these cells via the UTOPIA interface 120 to a physical interface board 138 comprising a plurality of (eg, eight) PHY portions 140 described below.

In addition to routing signal cells to upstream multiplexer 109, ATM interface 112 makes the supervisory information available to microprocessor 110. The upstream multiplexer portion 109 of the mux / demux portion 104 has an output port 102 connected to an optical transmitter source for transmitting the uplink transmission fiber 25 to the splitter site 23.

Within the physical interface substrate 138, the PHY portion 140 detailed in FIG. 6 is coupled to the UPOPIA interface 120 and operates to provide a physical interface to the ATM cell stream. PHY unit 140 provides the electrical interface, framing, synchronization and access protocols. The PHY unit 140 is bidirectionally connected to the hybrid circuit 146 through respective filters 142 and 144. Filter 142 operates to accept noise and interference in the received signal, and filter 144 operates to band-limit the transmitted signal. Hybrid circuit 146 operates to allow bidirectional transmission on a single unshielded twisted pair (UTP). The hybrid circuit 146 is ported to the UTP 148 through the brightness protection and power supply cross protection circuit 147 to prevent damage to the circuitry from an external source.

Referring to FIG. 6, the structure of each PHY transceiver portion is a speed adaptation, transmission (Tx) first-in, first-out elastic buffer (FIFO) in which a broadband service ATM data stream input from the UTOPIA interface 120 is connected through a transmission data link 153. Shown 150 with 150). The transmit FIFO buffer 150 operates to accommodate burst data arrivals and different data rates. It is read at a rate related to the output data rate of the port. The transmission Tx starting point of the cell (SOC) signal is connected to the transmission buffer 150 via the TxSOC link 155. The transmit enable and transmit clock signals are coupled to the FIFO 150 via links 154 and 156, respectively. The transmission full link 157 is used to indicate when the transmission FIFO 150 is complete.

Each read enable and read clock signal is coupled to buffer 150 via links 161 and 163. The read clock is transmitted from the timing generator 160 and the read enable signal is transmitted from the STS-1 framing unit 180. Timing generator 160 is coupled to receive the STS-1 reference 51.84 MHz clock from the UTOPIA interface. The 2: 1 cell multiplexer 170 is coupled to receive an SOC signal via a link 165, and the first input 171 of the multiplexer 170 is coupled to receive transmission data from the transmission buffer 150. The multiplexer 170 is stored in an auxiliary storage means (not shown) and has a second input 172 connected to receive a 'blank' cell without any cells queued in the transmission buffer 150. Multiplexer 170 also includes logic to generate and insert a cell header in the form of a header error correction mode (HEC) if the cell header is incomplete.

The output 175 of the multiplexer 170 is coupled to an ATM self-synchronizing scrambler 177 that operates to scramble the ATM cell payload to prevent false cell detection at the receiving device included in the user premise. The output of the self-synchronizing scrambler 177 is connected to an STS-1 framer 180 that operates to insert an ATM cell in an STS-1 frame, the format of which is shown in FIG. 2 above. The time slot counter 190 clocked by the subdivided framing clock (8 kHz / 3) supplied by the timing generator 160 provides a timing signal for inserting definable user F1 bytes in the STS-1 frame. The CPE ID lookup table 265 provided on the microprocessor interface 240 and read from the timeslot counter 190 based on the timeslot counter value provides the timeslot alignment value for transmission in F1 bytes.

As mentioned above, in accordance with the present invention, the F1 byte is used as a time slot assignment identifier for a bus return channel slotted from the CPE device. The output of the STS-1 framer 180 scrambles the STS-1 frame and transmits it to the user premise device via the UTP 148, and carries a carrierless amplitude modulation, phase modulation (CAP), such as a 16 CAP encoder. A standard SONET frame sync scrambler 192 that connects the scrambled frames to encoder 195. The output of the CAP encoder 195 is coupled to the transmit filter 142 via a link 197.

On the receiving side of the PHY transceiver portion, the output of the receive filter 144 returns, a CAP decoder 200, such as a 4 CAP decoder that operates to demodulate a burst of CAP modulated signals received from the user premise for the number of active slots in the uplink channel. Is connected via a link 198. Preferably, since the data rate of the slotted return burst signal is related to the transmission rate, frequency recovery at the receiver is required. Return channel bursts from the CPE must be scrambled and descrambled.

For this purpose, the output of the CAP decoder 200 descrambles the slotted return channel signal and is connected via a link 201 to a descrambler 210 that couples the descrambled signal to the burst demultiplexer 220. . Burst demultiplexer 220 operates to demultiplex ATM cells from return channel burst overhead. As described above with reference to FIG. 4, burst overhead includes information related to transmission monitoring.

The demultiplexed portion of the burst header is connected to associated header data registers, such as status register 225 and parity error counter 230, the contents of which are controlled by control microprocessor interface 240 through PHY subprocessor 250. To be monitored. Cell filter 260 discards empty cells to avoid wasting transmission resources. Receive FIFO 270 also operates to accommodate burst data arrivals and different data rates. It is read at a rate related to the output data rate of that port.

The reception start point of the cell (SOC) signal connected from the filter unit 260 via the line 271 is connected from the reception FIFO 270 via the RxSOC link 275. The receive enable and receive clock signals are coupled from the UTOPIA interface to the receive FIFO 270 via links 285 and 286. Receive buffer free link 287 is used to indicate when receive FIFO 270 is free. Each write enable and write clock signal is coupled to receive FIFO 270 via links 291 and 293. The write clock WR Clk is derived from the timing generator 160, and the write enable WR en signal is derived from the cell filter unit 260. The data is output over link 278.

7 diagrammatically illustrates the configuration of a communication unit or module 300 included in a user premise device such as a television set top box incorporating a transceiver change in accordance with the present invention to prepare for the ATM cell embedded STS signal format described above. At the downlink end of the UTP or coaxial cable, the CPE device has a hybrid circuit 301 that operates to allow bidirectional transmission on the cable 148. Filters 302 and 304 are connected to the hybrid circuit 301, respectively. Receive filter 304 operates such that no out-of-band energy is received from the received signal, and transmit filter 304 operates out-of-band emission where the transmitted signal may damage the receiver, broadcast service, or does not inadvertently follow FCC emission limits. To prevent the operation.

The output of the receive filter 302 is connected to the CPE resident PHY portion 310 detailed in FIG. 8 described below. The PHY unit 310 is connected to the ATM signal processing unit 320 via the UTOPIA interface 315. PHY portion 310 has a transmission port 312 connected to transmission filter 304 via driver 314. Each of PHY 310 and ATM signal processing 320 is coupled to supervisory control microprocessor 340 via bus 330. The output of the ATM unit 320 is connected to an MPEG decoder 331 which is connected to the microprocessor bus 330.

Referring to Figure 8, the configuration of each CPE-resident PHY transceiver section 320 is a CAP decoder 400, here 16 CAP modulated 51.84 Mb / s wideband received from the optical network section of Figure 6 on the downlink channel. Shown schematically with a 16 CAP decoder operative to demodulate the data stream. In the case of a signal loss (LOS), the LOS signal is coupled to the status register 410 via a link 352. The recovered 51.84 MHz clock signal is coupled to downstream circuitry via the recovered clock link 356. It is also connected to a divider 415 divided by 32 which generates 1.62 MHz for use in the transmission section of the network section.

The received data stream is coupled to an STS-1 framer 420 that fits on a SONET frame received via link 358 and performs a bit interleaved parity (BIP8) check on the data. Any error is connected to the B1 error counter 430 via link 362. It also applies a reset signal to the CAP decoder 400 via the link 367. In the case of frame loss (LOF), the LOF signal is coupled to the status register 410 via a link 364.

The STS framer 420 references the recovered clock on the link 356 to provide a receive byte clock of 6.48 MHz on the link 365 to the downstream signal processing element described below. The scrambled SONET data frame descrambles the downlink signal and connects the descrambled signal to the F1 byte detector 366 which extracts the F1 byte by examining the descrambled STS-1 frame overhead. 440 is connected. The detected F1 byte is coupled via a link 368 to a comparator 450 that uses the F1 byte to control the operation of the slot return channel described below.

The frame is also connected to a cell payload processor 460 using a pointer in the STS-1 overhead portion to identify a SONET synchronous payload envelope comprising the substantial data payload shown schematically in FIG. 2 above. . Cell payload processor 460 couples the start of a cell (SOC) signal on link 376 to receive FIFO 480. The data payload is coupled to a cell descrambler 470 that descrambles the cell payload and connects the descrambled payload data to the receive FIFO 480.

Receive FIFO 480 is an elastic buffer that accommodates burst data arrivals and different data rates. It is read at a rate related to the output data rate of the port. The receive enable and receive clock signals are coupled from the UTOPIA interface 315 to the receive FIFO 480 via links 385 and 386, respectively. Receive buffer free link 387 is used to indicate that receive FIFO 480 is free. Each write enable and write clock signal is coupled to receive FIFO 480 via links 369 and 365, respectively.

The rate adaptation, transmission FIFO 500 is coupled to receive an ATM cell from the UTOPIA interface 315. Transmit Tx start of cell (SOC) signal is coupled to transmit buffer 500 via TxSOC link 502. The transmit enable and transmit clock signals are coupled to the FIFO 500 via links 504 and 506, respectively. The transmit full link 507 is used to indicate when the transmit FIFO 500 is full. Respective read enable and read clock signals are coupled to transmit buffer 500 via links 511 and 513. The read clock is derived from divider 530 divided by 8 connected to divider 415 divided by 32 and the read enable signal is derived from comparator 450.

The data output path of the FIFO 500 is connected to a logic circuit 540 that operates to generate and insert a cell header in the form of a header error correction code (HEC), such as the multiplexer 170 in the PHY section of the optical network section. . The start of the cell SOC signal is connected via a link 541 to the HEC insertion logic 540 and cell capsule seal 550 that assemble the uplink return time slot including the overhead shown in FIG. 4 above. The bit error link 551 is coupled to the cell capsule seal 550 as part of the performance monitoring status byte containing information related to the condition of the CPE.

The output of the cell capsule sealing unit 550 is connected to an ATM self-synchronizing scrambler 560 that scrambles the ATM cell payload to prevent false cell detection at the receiver included in the user premise device. The output of the self-synchronizing scrambler 560 is clocked by the 1.62 MHz clock output of the divider 415 divided by 32, and the CAP- enabled by the transmit enable signal supplied on the link from the comparator 450. 4 is connected to the encoder 565.

As noted above, in accordance with the present invention, the F1 byte is used as a time slot assignment identifier for the bus return channel slotted from the CPE device with the detected F1 byte coupled to the comparator 450 via the link 368. In response to this detection, the F1 byte comparator provides a transmit enable signal to control when a return time slot occurs on the uplink channel. As such, 4 CAP uplink slot transmissions occur in bursts that synchronize or refer to the F1 bytes detected in the downlink STS-1 frame.

The generation time of the transmit enable signal generated by the comparator 450 is derived by the slot assignment stored in the associated time slot assignment table 570, which is then accessed via the microprocessor bus 590. Provided by microprocessor interface 600, which is coupled to status register 410 and B1 error counter 430. As described above, the output of the 4 CAP encoder 565 is connected to the transmission filter 304 through the driver 314 for application to the hybrid circuit 300.

For example, an initial time slot may be obtained by excluding one of the 64 time slots of FIG. 4 using the Aloha competition scheme for the initial time slot competition. By excluding a competitive time slot, it is possible to prevent a newly connected CPE from interfering with a CPE already in use. Once a newly added CPE requires a time slot, the assigned time slot may be used to request additional time slots as needed. These management functions may be accomplished by an external processor using the microprocessor interface 600.

9 schematically shows how the (unshielded twisted pair) multidrop link from the optical network section is interfaced with telephone and cable television signal ports generally provided in the user's premises. As shown herein, the frequency higher diplexer 600 is adapted to transmit an analog cable television signal to a first upstream port 601 to which the UTP 148 from the optical network section is connected and to the user premise. It has a second upstream port 602 to which the coaxial cable used by the provider is connected. The diplexer 600 further includes a second upstream, telephone signal port 603 to which the twisted pair 604 for the user premise telephone apparatus is connected. Diplexer 600 also includes a second downstream, coaxial cable port 605 to which a television set top box or standard cable ready television set is connected.

As shown as frequency spectrum isolation diagrams associated with each of its upstream and downstream ports, the diplexer 600 is received on the unshielded twisted pair 148 from the optical network interface and applied to the port 601. A 16 CAP modulated STS-1 base communication signal in the downstream direction and an analog cable television signal applied to the coaxial cable port 602 are operative to connect to the (broadband) coaxial cable output port 605. Coaxial cable output port 605 is a coaxial cable fanout connector portion that provides multiple coaxial cable feeds 607 to one or more user devices, such as set top boxes, VCRs, and cable ready television sets, as shown schematically in FIG. It is shown as connected to 606. Diplexer 600 also operates to connect a telephone signal received on a multidrop twisted pair to downstream telephone signal port 603.

In the upstream direction, the diplexer 600 is applied to the port 603 with the 4 CAP modulated STS-1 base communication signal in the upstream direction applied to the coaxial cable port 605 from the CPE-resident PHY portion of the set top box. The connected telephone signal to an unshielded twisted pair 148 to which an upstream port 601 is connected. 11 shows frequency spectrum separation of 16 CAPs in the downlink direction and 4 CAP ATM base communication signals in the upstream direction, and below the analog cable television signal band supplied to the diplexer coaxial cable port 602 by the cable television service provider. Indicates their dual separation.

As can be seen from the above description of the modification of the broadband communication system described in the '247 patent, each of the set top box and the optical network section related to the user premise of the system of the' 247 patent is prepared for the ATM cell embedded STS signal format. And F1 bytes, which provide the section overhead of the STS-1 frame, are used for the return channel timing reference. Thus, the present invention extends the use of internationally accepted standard communication protocols, in particular the use of a transmission standard of point-to-multipoint asynchronous transmission mode (ATM), in which ATM cell encapsulated STS base signals are broadcast to multiple user premise devices. can do.

As described in the embodiments according to the present invention, it is not limited thereto, and various modifications and changes may be made to those skilled in the art.

Claims (30)

A broadband that transmits a telecommunication message from a master site to at least one remote site and from the at least one remote site to the master site via a broadband communication path, wherein the at least one remote site is ported to the broadband communication path via a communication link. Transmit a downlink wideband information signal from the master site to the broadband communication path interface device and from the broadband communication path interface device to the one or more remote sites using a broadband communication system that is coupled to the communication path interface device. And transmitting a message signal from the at least one remote site to the broadband communication path interface device such that the message signal is transmitted to the master site. (a) generating, at the broadband communication path interface device, a first communication signal comprising a broadband information signal for at least one remote site at a destination and a representative return time slot control code associated with the destination remote site, wherein the multidrop communication is performed; Transmitting the first communication signal from the broadband communication path interface device to at least one remote site via a link; (b) at a destination remote site, detect the representative return time slot control code included in the overhead portion of the received first communication signal, convene a message signal as a second communication signal, and detect the representative And transmitting said second communication signal from said destination remote site to said broadband communication path interface device in a time-division slot format over said multidrop communication link for a time slot defined by a return time slot control code. How to. The method of claim 1, And said first communication signal comprises a synchronous optical network base communication signal. The method of claim 1, (a) incorporating the wideband information signal into the first communication signal as a data cell of a first fixed size with the representative return time slot control code; and the wideband communication path through the multidrop communication link. Transmitting said first communication signal from an interface device to said at least one remote site. The method of claim 3, wherein And wherein said first fixed sized data cell comprises an asynchronous transfer mode data cell. The method of claim 4, wherein And said first communication signal comprises a synchronous optical network base communication signal. The method of claim 3, wherein and (b) converging the message signal to the second communication signal as a data cell of a second fixed size. The method of claim 6, And said data cell of said second fixed size comprises an asynchronous transmission mode data cell. The method of claim 1, Wherein said at least one remote site corresponds to a single remote site in which a user premise broadband communication receiver is installed. The method of claim 1, And said at least one remote site corresponds to a plurality of remote sites on which each user premise broadband communication receiver is installed. The method of claim 1, Step (a) comprises inserting respective different representative return slot control codes associated with different remote sites into a common overhead of successive signals of the first communication signal, and step (b) Detecting, at each of different sites, different representative return time slot control codes included in the common overhead portion of the received first communication signal, and according to the detected representative return slot control codes. Transmitting a second communication signal during a defined respective different time slot. The method of claim 1, step (a) comprises transmitting the first communication signal to a lower first frequency band specifying a broadcast cable television signal, and step (b) designating a broadcast cable television signal from the first frequency band Transmitting said second communication signal in a spaced lower second frequency band. The method of claim 11, The destination remote site further comprises a coaxial cable port to which a cable television signal is supplied from a cable television service provider and a telephone signal port to which a user premise telephone device is connected at the destination remote site, step (b) A cable port for connecting the first communication signal and a cable television signal received on the multidrop communication link to a broadband output port and for connecting a telephone signal received on the multidrop communication link to the phone signal port. Coupling a diplexer filter with the coaxial cable port and the multidrop communication link. The method of claim 11, Step (a) includes transmitting the first communication signal as a first carrierless amplitude modulated phase modulated signal, and step (b) transmits the second communication signal as a second carrierless amplitude modulated phase modulated signal The method comprising the step of. The method of claim 1, And wherein said multidrop communication link has an unshielded twisted pair. A broadband that transmits a telecommunications message from a master site to at least one remote site and from the at least one remote site to the master site via a broadband communication path, wherein the remote site is ported to the broadband communication path via a multidrop communication link. Using a broadband communication system to be coupled to a communication path interface device, transmitting a downlink wideband information signal from the mast site to the broadband communication path interface device and from the broadband communication path interface device to the one or more remote sites; In an arrangement in which a message signal is transmitted from the one or more remote sites to the broadband communication path interface device such that the message signal is transmitted to the master site. Generate within the broadband communication path interface device a first communication signal comprising a broadband information signal specifying at least one destination remote site and each representative return time slot control code associated with each destination remote site; An upstream transceiver operative to transmit the first communication signal from the broadband communication path interface device to the at least one remote site via the multidrop communication link; Installed at each destination remote site and operative to detect each representative return time slot control code included in the overhead portion of the received first communication signal, convening a message signal as a second communication signal, and Transmitting the second communication signal from each destination power site to the broadband communication path interface device in a time-division slot format over the multidrop communication link during each time slot defined in accordance with the representative return slot control code detected. An arrangement comprising a downstream transceiver. The method of claim 15, And said first communication signal comprises a synchronous optical network base communication signal. The method of claim 15, The upstream transceiver inserts the wideband information signal into the first communication signal as a data cell of a first fixed size with the representative return time slot control code, and from the broadband communication path interface device through the multidrop communication link. And transmit the first communication signal to the one or more remote sites. The method of claim 17, And said first fixed sized data cell comprises an asynchronous transfer mode data cell. The method of claim 18, And said first communication signal comprises a synchronous optical network base communication signal. The method of claim 19, And said downstream transceiver is operable to bring said message signal into said second communication signal as a data cell of a second fixed size. The method of claim 20, And said second fixed sized data cell comprises data cells in an asynchronous transmission mode. The method of claim 15, Wherein said at least one remote site corresponds to a single remote site. The method of claim 15, Wherein said at least one remote site comprises a plurality of remote sites. The method of claim 15, The upstream transceiver is operative to insert each different representative return slot control code associated with a different remote site into a common overhead of successive ones of the first communication signals, the plurality of downstream transceivers each having a different remote location. Different time slots installed at a site and detecting the different representative return time slot control codes included in the common overhead portion of the received first communication signal and defined according to the detected representative return slot control codes. Arranged to transmit a second communication signal during the communication. The method of claim 15, The upstream transceiver is operative to transmit the first communication signal in a lower first frequency band that specifies a broadcast cable television signal, and the downstream transceiver specifies a broadcast cable television signal and is spaced apart from the first frequency band And transmit the second communication signal in a lower second frequency band. The method of claim 25, The destination remote site further comprises a coaxial cable port to which a cable television signal is supplied from a cable television service provider and a telephone signal port to which a user premise telephone device is connected at the destination remote site, wherein at the destination remote site, A broadband output port coupled to the coaxial cable port and the multidrop communication link for applying the first communication signal received on the multidrop communication link and the cable television signal at the coaxial cable port to the downstream transceiver; And a diplexer filter coupled to and operative to connect a telephone signal received on the multidrop communication link to the telephone signal port. The method of claim 26, The upstream transceiver is operative to transmit the first communication signal as a first carrierless amplitude modulated phase modulated signal, and the downstream transceiver is operable to transmit the second communication signal as a second carrierless amplitude modulated phase modulated signal Array characterized in that. The method of claim 15, And wherein said multidrop communication link has an unshielded twisted pair. The method of claim 15, The upstream transceiver is operative to receive the second communication signal transmitted by the downstream transceiver and to transmit the message signal contained therein to the master site via the broadband communication path. The method of claim 15, The upstream transceiver receives the second communication signal transmitted by the downstream transceiver, transmits a first selected message signal contained therein to the master site via the broadband communication path, and the broadband communication path interface. Arranged to extract a second selected message signal contained therein for use with the device.